Percussive tools



June 29, 1955 K. M. ELLIOTT ErAL 3,191,694

PERCUSSIVE TOOLS Filed March 5, 1962 8 Sheets-Sheet 2 June 29, -1965 K. M. ELLIOTT ETAL 3,191,694

PERCUSSIVE TOOLS 8 Sheets-Sheet 3 Filed March 5, 1962 Lr. m MW k/ \M\w\\\\\\\\\\\\\\\\\ @NUN 8 Sheets-Sheet 4 K. M. ELLICTT ETAL PERCUSSIVE TOOLS June 29, 1965 Filed March 5, 1962 June 29, 1965 K, M. ELLIOTT ET AL PERCUSSIVE TOOLS 8 Sheets-Sheet 5 Filed March 5, 1962 June 29, 1965 K. M. ELLIOTT ErAL 3,191,694

Pnncussrvn TooLs Filed March 5, 1962 8 Sheets-Sheet 6 June 29 1955 K. M. ELLlo-r'r ETAL 3,191,694

PERCUSSIVE TOOLS 8 Sheets-Sheet '7 Filed March 5, 1962 June 29, 1965 n M. ELLIOTT ETAL 3,191,694

PERCUSSIVE TOOLS Filed March 5, 1962 8 Sheets-Sheet 8 United States Patent O 3,191,694 PERCUSSIVE 'IOLS Kenneth Malcolm Eiiiott, High Barns, Sunderland, and George Vincent Beil, Ponteland, Newcastie upon Tyne, England, assignors to .lohn Lynn 8l Co. Limited, Pailion, Sunderland, Engiand, a company of Great Britain and Northern Ireland Filed Mar. 5, 1962, Ser. No. 177,589 16 Claims. (Ci. 173-161) This invention relates to percussive tools of the kind used for breaking stones, concrete, road surfaces or the like, or for drilling, routing or channeling or like operations in concrete, brick or other surfaces of walls, floors and the like, or for chipping, scaling or dressing of metal castings, or rivetting, caulking, or scraping, also for vibrating or compacting, or pile-driving or digging. More particularly the invention relates to percussive tools of the aforesaid kind which are adapted to be operated by a liquid under pressure, and wherein the operation is effected solely by liquid pressure.

Hereinafter for convenience the tools which are the subject of the invention will be referred to as hydraulic percussive tools.

An object of the invention is to provide a hydraulic percussive tool which is highly efficient and operable by a liquid under pressu-re with a high rate of striking and a balanced motion that reduces the vibration of the hammer casing. Such a tool is advantageous in that it dispenses with an air compressor, and can be operated from readily available hydraulic supply means, such as that provided, for example, on a tipping lorry for the operation of the lifting ram thereof.

The invention provides a hydraulic percussive tool having two hammers reciprocable to engage a single anvil, each of said hammers being connected with one of two pistons, said pistons being located in cylinders having on corresponding sides of their pistons intercommunicating like spaces to constitute a closed balance chamber which is lilled with hydraulic Huid whereby as one piston is forced in one direction the other piston is correspondingly forced in the other direction, and hydraulic control means whereby spaces on the opposite corresponding sides of the pistons are alternately connectable respectively with supply and exhaust ducts for hydraulic iiuid The two hammers may be housed in a single casing. Each hammer may be slidably guided partly by the inner surface of said casing and partly by at least one longitudinal surface of the other hammer, so that the hammer heads alternately engage a single anvil located (in known manner per se) at one end of the casing, whereby the hammer blows are transmitted to a pick, chisel or other tool slidably received in a socket secured to said one end of the casing. For example, the casing may be cylindrical, and each hammer may be semi-circular in transverse section so that it partly guides and is partly guided by the diametrical face of the other; or with a view to providing that each hammer head shall engage the anvil more concentrically, one hammer may have a horseshoe or U-section and the other a mushrom or T-section, the two sections mating to provide a joint polygonal or cylindrical periphery. In another mode, the hammers may each be rectangular in section and housed in a casing which is also rectangular in section.

The hydraulic control means may comprise a control valve operable at will, as by trigger means, through a resilient lost motion device or element such as a compression coil spring, to initiate the actuation of the pistons, and means whereby said valve is automatically displaceable under the joint and opposite reciprocation of the pistons to cause annular chambers of the hydraulic ICC cylinders surrounding the piston rods to be connected alternately to hydraulic liquid supply and exhaust ducts.

Embodiments of tools according to the invention will be described with reference to the accompanying drawings, wherein:

FIG. 1A is a diagrammatic axial section of the head of one embodiment of hydraulic percussive tool,

FIG. 1B is a corresponding axial section of the pickreceiving end of the same, and

FIG. 2 is an elevation, corresponding to FIG. 1A and partly in radial section on the line II-II of Said FIG. 1A;

FIGS. 3A and 3B comprise a longitudinal section, on the line Z-Z of FIGS. 4A, 4B, of another embodiment of hydraulic percussive tool,

FIG. 4A is a side elevation, partly broken away and in section on the lines Y-Y, X-X, W-W, V-V and T T of FIG. 3A,

FIG. 4B is a side elevation, partly broken away and in section on the line S-S of FIG. 3B,

FIG. 5 is a transverse section on the line R--R of FIG. 3B,

FIG. 6 is a fragmentary longitudinal section on the line P-P of FIG. 3A,

FIG. 7 is an isometric view, in section partly on the plane of line V-V of FIG. 3A and partly on the median plane perpendicular thereto.

FIG. 8 is a transverse section on the line N-N of FIG. 3A,

FIG. 9 is a fragmentay longitudinal section on the line O-O of FIG. 8,

FIG. l0 is a plan view of the shuttle valve housing,

FIG. 11 is an axial section on the line M-M of FIG. 10.

FIGS. 12 and 13 are transverse sections respectively on the lines L-L and K-K of FIG. 11, and

FIG. 14 is a section of the shuttle value end cap.

The hydraulic percussive tool as shown in FIGS. 1A, 1B and 2 comprises a cylindrical casing 1 wherein are slidably located two hammers 2 and 3, each iof which is semi-circular in transverse section, so that said hammers are slidably guided partly by the inner surface of the casing 1 and each partly by the diametrical surface of the other. As shown in FIG. 1B, the hammersZ and 3 are respectively provided with head 4 and 5 each to engage with a sharp impact, an anvil 6 which is located in a manner already known at the inner end of a socket member 7, secured tothe end of the casing 1 by a screwed ring t5, said socket serving Ato receive and guide a pick Ior like tool 9; the arrangement is such that when the tool 9 is caused to bear upon the work, it displaces the anvil from its seat, and as said anvil is repeatedly struck by the hammer heads 4 and 5 the tool 9 is thereby caused to strike the work with a rapid series of blows.

Referring now to FIG. 1A, it will be seen that each of the hammers 2 and 3 is connected with a piston rod, for example by T-slots 10, 11 in the hammers 2 and 3, and T-heads 12, I3 on the piston rods 14, 15, as diagrammatically shown. The piston rods 14, 15 pass through registering holes formed in a resilient butter gasket 16 and a partition plate 17 located at the upper end of the cylinder 1, into two parallel cylinders 18, 19, wherein the piston rods are provided respectively with pistons 20, 21. The heads :of the cylinders 18 and 19 are closed by a cap 22 having an internal recess 23 whereby said cylinder heads are interconnected to form a balance chamber, which is completely filled with a hydraulic fluid. The cylinders 18, 19 are bored in a cylindrical block 24, which is secured to the casing 1 by a screwed ring 25 the plate 17 being located by an external liange thereon between the upper end of said casing 1 and the lower end of said block 24.

Within the cylinders 13, 19, and about the piston rods 14, there are formed annular chambers 26, 27 closed at their upper ends respectively by the pistons 20, 21, and closed at their lower ends by bushes 2S, 29, which are secured between the plates 17 and annular shoulders formed adjacent the lower ends of said cylinders.

Control means for hydraulic actuation of the hammers 2 and 3 is illustrated in FIGS. 1A and 2. ,As shown in FIG. 2, the cylinder block 2,4 is provided at its upper end, in a plane at right angles to the plane of the axes of the cylinders 18, 19, with two projecting handles 3i), 31. On the handle 3) is pivotally mounted a trigger 32 which bears upon a push-rod 33 slidable through a diametrical hole in the handle 30, and at its lower end in a bush 34 in a valve block 35. A spring 36 mounted over pushrod 33 bears on a fixed support ring 37 and presses against a collar ring 3S mounted on rod 33 and retained -on said rod by screw 39. The valve block has a bore 40, in one end of which the bush 34 is located, said bore being provided with four annular enlargements 41, 42, 43 and 44. Within the bore is located a cylindrical slide valve 45, having an annular recess 46 at its middle, and two peripheral land surfaces 47, 4S at its ends. The valve 45 is mounted on a spindle 50, and has, longitudinal passages 51 by way of which hydraulic iluid can pass through the interior of the valve for the purpose to be described. The upper end of the spindle 50 has a head 52 located in the bore in the bush 34, wherein the push-rod 33 is slidable, said head 52 and the lower end of the ypush-rod being separated by suicient distance to allow independent movement of both, and a compression coil spring 53 housed within a bore in the push-rod 33, bearing upon said head. The lower end Vof the spindle 50 is located in a blind axial bore 54 in a closure member 55 for the lower end lof the bore 4t) in the valve block 35, and said bore 54 has at its base a lateral branch 56 which communicates by a passage 57 in the valve block with the interior of the member 24.

As shown in FIG. 1A, the two bushes, 2S, 29 are provided with annular series of radial ports 58, 59. In the relatively thin portion of wall 60 separating these bushes is formed a transverse aperture 61 in communication With one each of the ports 58, 59, and this aperture 61 isl connected by a radial passage 62 with the duct 57 in the valve block.

In said valve block, the annular enlargement 41 is connected with an exhaust duct for hydraulic fluid, the enlargement 42 is connected by way of a passage 63 with a port 64 in the cylinder 18 adjacent the bush 2S, the enlargement 43 is connected with a supply duct for hydraulic huid, and the enlarge-ment 44 is connected to a port 65 in the cylinder 19, adjacent the bush 29, by way of a passage 66. Further, there are provided in the bushes 23 and 29 respectively ports 68, 69, the former being permanently connected to the exhaust duct, and the latter permanently connected to the supply duct for hydraulic iuid; and in each of the piston rods 14, 15, adjacent the pistons 20, 21, there is formed a pair of longitudinally spaced cruciform passages 70, 72, 71, 73. Y

The operation of the device will now be described. The pistons 14, 15 and the valve 45 are shown in neutral location. When the trigger 32 is depressed, the spring 53 pushes the valve spindle 50 down and displaces the valve l5V to put the supply port 43 in communication with the port 64- in the annular space 26, at the same time putting the port 65 in the annular space Z7, which is connected with the enlargement d4, thence through the passages 51 in the valve, into communication with the exhaust port 41. Thus the entry of pressure tluid by the port 64 into the annulus 26 acts upon the piston 20 to push it upwards and thereby raise the hammer 2. At the same time, the annulus 27 being open to exhaust the displacement of uid bythe piston in the balance chamber, constituted by the cylinder heads 18 and 19 inter-communicating by 4 Way of recess 23, forces the piston 21 downwards, and causes the head 5 of the hammer 3 to strike the anvil 6. The movement of the piston 21 continues until the cruciform holes 71, 73 register with the ports 59 and the port 69 in the bush 29, whereby pressure fluid from the port 69 is transmitted through said ports 59, the aperture 61 and the passages 62, 57, 56 into the lower end of the bore 54, where such pressure fluid acts upon the lower end of the valve spindle 5G to compress the spring 53 and displace the valve 45 to its other limit position, thereby reversing the mechanism. The valve in this position puts the pressure supply port 43 in communication with the enlargement 44 in the valve block, and thence by way of the passage 66 with the port 65 in the wall ofthe annulus 27, while at the same time the exhaust port 41 is put into direct communication with the enlargement 42 and thence by Way of the passage 63 with the port 64 in the wall of the annulus 26. Thus the piston 21 is forced upwards, and thereby displaces fluid in the balance chamber to drive the piston 20 downwards and cause the head 4 of the hammer 2 to strike the anvil 6.

At trie end of the stroke, the crucit'orm holes 70 and 72 in the piston rod 14 register with the ports 58 and 623 in the bush 28, thereby putting the exhaust duct connected with said port 5S into communication, through the aperture 61 and the passages 62, 57, 56, with the bore 54. This relieves pressure at the lower end of the valve spindle Sil, and allows the spring 53 to displace the valve 45 to its lower limit position, thus completing the cycle and commencing a further cycle as above described.

`When the trigger 32 is released spring 36 lifts the rod 33 by means of collar 3S and retains the valve 45 in neutral location.

It will be appreciated that with a suitable pressure of the Huid supply the operation of the hammers will cause the anvil 6 to exert upon the pick 9 a very rapid series of blows, which contributes to the efciency of the apparatus.

Referring new to the embodiment illustrated in FIGS. 3A, 3B, 4A, 4B and FlGS. 5-9 of the accompanying drawings, the arrangement is essentially similar. In the hydraulic percussive tool shown in these drawings, the casing 151 is rectangular (as shown more particularly in FlG. 5) and encloses two hammers 102 and 103 each of which is also rectangular in cross section. These hammers are slidably guided each by a pair of longitudinal rods 74, '75, the hammers having each two pairs of slipper half bushes i7 located by set screws 7S. The rods 75 have screw-threaded ends, the upper ends 79 being screwed into tapped holes in a cylinder block 124 so as to secure a seal plate 117 between said cylinder block and the casing 151, and the lower ends of said rods being engaged by nuts 75 so as to secure to the lower end of the casing 101 an anvil guide socket 107. The hammers 162 and 1533 are located to engage each with a sharp impact an anvil located in the inner end of the guide 167. Said socket also serves to receive and guide a pick or like tool 199. rl`he arrangement is such that when'the tool 159 is caused to bear upon the work it displaces the anvil 166 inwardly, and as said anvil is repeatedly struck by the hammers 102, 1193, the tool 199 is thereby caused to strike the work with a rapid series of blows. Outward displacement of the anvil under the hammer strokes is limited by a resilient buffer ring Si? located upon an internal shoulder in the socket 107. Dislodgernent of the tool 159 from the socket 157 is prevented by a transverse, tangential stop pin S1 to which is secured a lever S2. The pin 31 has a recess which permits entry into the socket 107 of a shoulder 83 on the shank of the tool 159 and thereafter the pin is turned by a torsion spring 84 so as to be engaged by said shoulder if the tool shank tends to come out of the socket.

As shown in FlGS. 3A and 4A, each of the hammers 162, 103 isconnected with one of a pair of piston rods,

114, 115, each hammer having a T-slot 111 in which is engaged a T-head 113 on the piston rod. The piston rods 114, 115 pass through sealing rings 116, located in the seal plate 117, into two parallel cylinders 11S, 119 wherein the piston rods are provided respectively with pistons 120, 121 each secured to the end of its respective rod by a set bolt 84. Between the head ends of the cylinders 118 and 119 is a transverse passage 123, and the conjoint outer ends of the cylinders and said passage are closed by a buffer member 85 of suitable resilient material. This buffer member is seated in a recess in the internal face of a cap member 122 which bears upon the upper end of the cylinder block 124. The space comprised between the pistons 120, 121, and the butler member 85 together with the transverse passage 123 is completely filled with a hydraulic fluid, whereby the cylinder heads are interconnected to form a balance chamber.

Within the cylinders 118, 119 and about the piston rods 114, 115 there are formed annular chambers, such chamber 127 in the cylinder 119 being shown in FIG. 3A, and the other being identical therewith. These chambers are closed at their upper ends by the pistons, and at their lower ends by bushes, of which the bush 129 is shown in diametrical section in FIG. 3A and partially in plan, in FIG. 4A, While the like bush 128 is shown partially in radial section in FIG. 4A. Each of these bushes is located against the seal plate 117 with a seal ring 86, by a tight rit in the inner end of the cylinder bore, aided by the internal hydraulic pressure.

As shown in FIG. 3A, the cylinder head cap 122 is provided, in a plane at right angles to the plane of the axes of the cylinders 118, 119 (that is, the plan indicated by the section line O O, FIG. 8) with two projecting handles 130, 131. In a recess 87 in the handle 138 there is pivotally mounted a trigger 132 on a pin 88, said trigger having a nose 89 which bears on a push rod 133 slidable through a hole in the handle 131) and at its lower end in a bush 134 secured to a vaive block 135. A spring 13e mounted within the bush 134 about a control valve 125, which is borne upon by the push rod 133, is abutted between a face 137 of the valve blocl; (FIG. 7), and a collar 138 on the upper end of 'said valve 125. The valve block 135 has three parallel, blind, co-planar bores. In the middle one of these bores, which is co-axial with the bore in the bush 134, there is located a control valve insert 9). In the outer pair of bores are located a pair of plungers 98, 99 each resiliently loaded by a spring 91, coaxially housed therein and bearing on the face of the bush 134. Each of these plungers is biassed to close entry to one of a pair of longitudinal blind extensions 92, 93, from one of a pair of blind, outwardly extending bores 94, each of the bores 94 being in communication with one of a pair of internally screw-threaded holes 95 open to the exterior of the valve block 135. The vbores 94 open to the lateral face of the valve block 135, where they register with a pair ot oblique bores 96 in the cylinder block 124 for a purpose which will be described below. The extension 93 is connected by a transverse passage 97 with a lateral bore 19d, with its axis in the median plane of the block 135, which registers with a lateral port 165 in the cylinder block 124, while the extension 92 communicates through a similar lateral bore with another lateral port 194 in the cylinder block, which has its axis olset in the same longitudinal plane as said plunger 98.

Said ports 164, 185 enter a larger transverse bore 188 in the cylinder block 124, in which is housed a shuttle valve housing 175, illustrated in detail in FIGS. 10-13. Said housing is a casting or moulding having end flanges 176 with annular recesses for seal ring, whereby it is located radially in said bore 108, and two arcuate recesses 177, which are engaged in register with the cylinders 118, 119 by the bushes 128, 129, to locate said housing endwise. The housing has an eccentric bore 178 in which is 6 located for free sliding a shuttle valve 179 (FIGS. 3A, 4A). Between the flanges, said housing is constituted by an eccentric arch portion 18@ carrying a median boss 181 having a bore 182 which registers with the port 165 in the cylinder block. On the same side as said boss, the arch portion 1807is separated from the anges by two transverse ports 183, being connected to said anges by opposite arcuate portions 184.

The shuttle Valve 179 slidable in said housing 175 is in the form of a spool with two spaced pistons 185, 186. There extends into a blind bore 187 Within the piston portion 186 a stem 189 of a valve end cap 188, shown partly in longitudinal section in FIG. 4A and in transverse section in FIG. 14. Said stem 189 extends from an obturator portion 190 with an annular recess 191 for a seal ring, serving to' close the open end of the bore 178 in housing 175. Said valve end cap has an axial blind bore 192 extending from and plugged at its outer end, the inner end of said bore registering with two radial ports 193 adjacent the inner end of the stern, which ports co-operate with a pair of annular recesses shown in the shuttle valve 179 in FIG. 4A, within the bore 187 thereof and located within the axial dimension of the piston 186. Said bore 192 communicates with a radial bore 193, also plugged at the circumference of the cap 188, the bore 193 in turn communicating with a port 194 in the inner face 195 of said cap whereby it is located against the lateral surface of the cylinder block 124. This port 194 registers with a transverse drilling in the cylinder block, below the housing 175, which drilling communicates with a longitudinal blind bore extending to and plugged at that face of the cylinder block which engages the seal plate 117; said 1ongitudinal bore also traverses another lateral bore drilled into the cylinder block adjacent said face thereof, also plugged at its outer end and extending through the inner ends of the cylinders 118, 119, which are occupied by the bushes 128, 129. These bores are located in a plane parallel to the plane of the axes of said cylinders, and the position of the last-mentioned transverse bore 161 is indirx ed by chain-dot lines in FIG. 8, While a portion of said bore which extends through the thin wall 160 between said bushes is shown in FIG. 4A.

Reverting now to the control valve 125, as shown in FIGS. 4A and 7, and the insert 9i) in which it is displaceable, it will 4beseen tha-t said valve comprises an inner portion with an axial bore 139 extending to a diametrical bore 140 beyond which the valve is provided with a seal ring located in an annular recess. About the portion of said valve body through which the axial bore 139 extends said body has a shallow and relatively long circumferential recess 197. Said recess is adapted to co-operate with and interconnect (in the position of the valve shown in FIGS. 4A and 7) two annular enlargements 141, 142 separated by a land 143 in the insert 99, and said transverse bore 140, is, when the Valve is depressed by the trigger 132, adapted to co-operate with the recess 141. The bore 139 opens into the end portion of a bore 144 in which said control valve is located, and which communicates by an axial port 145 with a diametrical passage 146, in enlarged ends of which are located balls 147, 148 serving as automatic one-Way valves which close by inward displacement. More remotely from the valve 125, the insert 90 has another diametrical passage 149 with reduced end ports, one of which is formed by an apertured plug to permit location in the larger central portion of a ball 150, adapted by displacement to close either of said end ports while opening the other. As shown in FIG. 7, the passage 149 is intersected by a third diametrical passage 151, the ends of which open into a pair of longitudinal recesses 152 which serve as transverse ports connecting the larger central portion of passage 149 with radial drillings that intersect the annular enlargement 142. Also the enlargement 141 is opened into by opposed ra dial drillings 153, parallel to the passage 151, which connect said enlargement with an annular recess 154 in the wall enclosing the insert 99, which recess breaks through into the bores housing the plungers 98, 99. In register with said breakthrough, each of the plungers 98, 99 has an annular reduction 155, having a length greater than the possible plunger displacement, and connected by a radial port (not shown) with the bore in which the spring 91 is housed. Furthen'each of the bores in which the plungers 98, 99 are located has, where it interesects the outwardly extending bore 94, an annular enlargement 156, these enlargements both breaking through the Wall enclosing the insert 9!) to register with the ends of the first and second transverse passages 146, 149 in said insert.

Further as shown in FIGS. 4A and 8, the cylinder block 124 has extending from its face abutted by the head cap 122, a longitudinal blind bore 157 closed at said abutting face by a sealing screw This bore 157 interconnects two lateral drillings 162, 163 (plugged at their outer ends) which respectively intersect tangentially slight annular enlargements 164, 165 in the cylinder 119 (see also FIG. 3A). The cylinder block 124 also has another longitudinal bore 159, as Shown in FIGS. 6 and 8, extending through it and closed at both ends by sealing screws 158. Near its inner end this bore 159 is entered by a plugged lateral drilling 166, which intersects an annular groove 167 adjacent the outer end of bush 129; which communi- Cates, by opposed radial ports 215, parallel to the drilling 166, with'thebore of the bush 129. Adjacent its outer end, the bore 159 is entered by a plugged lateral drilling 163, which intersects tangentially a slight annular enlargement 169 in the cylinder 11S. The bore 157 houses a valve ball 216 which prevents liuid wo.4ufETAOIN valve ball 216 which prevents uid flow from drilling 162 to drilling 163 and bore 159 houses a valve ball 217 which prevents lluid flow from drilling 168 to drilling 166.

Each of the bushes 12S, 129 as shown in diametrical section in Fig. 3A and partly in elevation in FIG. 4A, has said annular groove 167 adjacent its outer end, and also a second annular groove 170 towards its inner end, and a third annular groove 171 at its middle. The annular grove 167 of the bush 128 has no function. The annular grooves 17d are interconnected by the transverse bore 161, and each connects with the bore of its respective bush by two opposed radial ports 172 (FIG. 4A). The middle grove 171 of bush 129 communicates with the bore of the bush by way of opposed radial ports 173, and also by drillings (partly shown at 174, FIG. 4A) with the middle port 165 in the cylinder block which opens to the shuttle valve housing,V While the middle groove of bush 128 similarly communicates with the bore of its bush and is connected by drillings (not shown) with the odset port 1634 in the cylinder block which also opens to the shuttle valve housing. Each of the pistou rods 114,115 has an annular reduction 196 which, as the piston moves to the inner end of its stroke, registers successively with the radial ports of its bush 12S or 129, to connect the middle groove 171 in said bush alternately with the inner groove 17d or the outer groove 1&7.

The cylinder block 124 incorporates a duplicate pneumatic buffer system. Each of the passages j (FIG. 3A) opens into one of a pair of cylinders 193, each of which extends to the face of the cylinder block which is engaged by the head cap 122. Within each of theL cylinders 198 there is located a llexible cylindrical bag 199 of impervious material such assynthetic rubber. This bag is secured in the end of the cylinder 19S, by an internal liange which abuts the face of the cap 122, by means of a retainer member 200, Whchhas a conical face coaxial with a central bore, and a screw-threaded spigot 2191 that is engaged in a suitable tapped hole in the head cap 122. At its end directed towards the passage 96 the liexible bag `199 is closed by -a separator valve member 2192 having a conical projection that enters the passage `96, extending from a `disc 2133 having a boss on which is riveted a second disc 204, so that au internal flange at this end of the bag 199 isgsecured between the two discs to close the interior of the bag. Said interior of each of the two bags 19@ communicates with another parallel cylinder 265 by way of a transverse passage 2% in said head cap 122, the joint between the cylinder 225 and said head cap being made airtight by a seal ring 29"/ which is secured against the face of said cap by another of said members Zilli engaged in a corresponding screwthreaded aperture in said head cap. Coaxially with the cylinder 265 the head cap 122 has a bore comprising a small central portion 2113, and an inner enlargement 209 which is open to the passage 236 and an outer enlargement 21% which is screw-threaded and closable by a screwed plug 211. The small portion of the bore 26S is entered by a conical nose of a filling valve 212 which has a shoulder 213 carrying a seal ring 214 that seats upon the face of the enlarged portion of the bore 259. The collar 213 also serves as an abutment for a compression coil spring, the other end of which bears against an internal shoulder in the bore of the member 2% which is located in the cylinder 2115. Upon removal of the plugs 211, each of the duplicate systems comprising the interior of a bag 199, one ofthe cylinders 205 and the connecting passage 2da can be charged with compressed air. The entry of compressed air is permitted by displacement from its seat of the seal ring carried by the valve collar 213, but as soon as the yfilling has been completed to the desired pressure, the valve re-seats itself and permits withdrawal of the nozzle element of the charging means from the screw-threaded aperture 211 without loss of internal pressure, whereafter the plug 211 can be inserted to prevent accidental opening of the valve. This arrangement thus provides Va pair of pneumatic accumulators charged by a pressure corresponding to the hydraulic pressure employed, and affording resilient buffers by reason of the compressibility of the air and the exibility of the bags 199.

For the operation of the tool as described with reference to FIGS. 3-14, it is required that the chamber 127 about the piston rod shall be connected alternately to a source of hydraulic fluid under pressure and to exhaust, while the corresponding chamber about the piston rod 114 (which is not illustrated but for convenience will be designated chamber 125) is simultaneously connected alternately to exhaust and supply source. Access to said chambers 126, 127 is by way of the shuttle valve housing 175 under control of the valve 179. When this valve is at the blind end of the bore 178, as shown in FIGS. 4A and ll, the chamber 127 is in communication with the central pmt 165 by Way of bore 182 in said housing, while the working chamber 126 is in communication with the oli-set port 14.34 by wayV of the left hand port 183 in the housing 175. Of course, when the shuttle valve moves to the other end of the bore 178, these channels of communication are reversed.

To cause operation of the tool, the control valve 125 is depressed by the trigger 132 operating through push rod 133, thereby bringing the diametrical bore in said valve into register with the enlargement 141 in the central valve insert 95.). This puts said enlargement 141 by way of the axial bore 139 of valve 125 and the axial port 145 into communication with the diametrical passage 145. Through the drillings 153 said enlargement 141 is permanently in communication with the annular recess 154- surrounding said insert 90, which recess is `open into the bores housing the plungers 923, 99, in permanent register with the annular reductions 155 in said plungers. Thus, when the control valve 125 is depressed, l'luid located behind and within both plungers is enabled to pass, by way of the radial ports from their bores, through the reductions 155 in said plungers and by way of 141, 139, 145 to the passage 146. This fluid escapes, by moving one of the balls 147, 143 from its seat in the passage 146, to the other enlargement 156 which is connected to exhaust. Fluid under pressure having access '9 to either of the enlargements 156 cannot enter the passage 146, since it closes upon its seat the other of the balls 147 or 148 in the adjacent end of said passage.

The diametrical passage 149 in the valve insert 90 serves to atto-rd entry of iluid under pressure within and behind the plungers 98, 99 when the control valve 125 is in its inoperative position Vas shown in FIGS. l4 and 7. Hydraulic uid ysupplied -to the enlargement 156 surrounding either of the plungers 9S, 99 (notwithstanding that said plunger is seated) displaces the ball 150 to its seat at the opposite end of said passage 149, so that said liuid cannot escape to exhaust. -From said passage 149 the duid passes by way of the intersecting diametrical passage 151 land Itransfer passages 152 (FG. 7) to the annular enlargement 142 in said insert 90. In the inoperative position of valve 125, said enlargement 142 is in communication, by the annular recess 197 in the control valve, with the enlargement 141, .and by the drillings 153 with the annular recess 154 and the reduction 155 in the plungers 98, 99 and thence by the radial drillings therein with the interiors of the plungers and the base ends of the bores in which they are located, so that while the tool is inoperative, both of the plungers 90, 99 -are locked on their seats by the full hydraulic pressure. When the valve 125 is depressed to its operative posi-tion, communication between the enlargements i141, `142 is prevented, by engagement with the intervening land `143 of the peripheral surface of valve 125 immediately below the transverse bore 140, and iluid from within and behind both plungers passes as described to exhaust, so that these plungers are during opera-tion of the tool biassed only by the springs 91.

Assuming that the port 105 is lsupplied with hydraulic llluid under pressure, by way of ducts 100, 97, 93 and those of the pairs of bores 94, 95 connected with said duct 93, as shown in FIGS. 3A tand 7 (the plunger 99 being thereby displaced from lits seat) the piston 121 is urged by said fluid to the outer limit of its stroke, so that by displacement of tluid in the balance chamber (cylinders 119, 11S and transfer passage 123) the other piston 120 with its rod 1,14 and associated hammer 102 is driven inwards, land the hammer 102 strikes the anvil 106.

As the piston 120 moves inward (under the transfer of Huid in the balance chamber caused by outward movement of the piston 121) duid from the Working chamber -126 of said piston 120 is freely displaced to exhaust through the lett hand port 183 of :the shuttle valve housing 1175 and the ott-set port 1434 in the cylinder block, being able -to depress plunger 98, against its spring 91 only, to gain laccess to that one of the ports 95 which is connected to exhaust.

As the piston 120 moves inwards to its inner limit, the annular reduction 196 in the piston rod 114 provides a channel for fluid between the inner and middle grooves 170, 171 of the bush 128 by Way of radial ports 172, 173, Since the ports 172 are in communication, by way of the drilling 161 in the cylinder block and the drillings in the valve head cap 18S, with the bore -187 in the shuttle valve 179, `and the ports 173 :are in communication with the oit-set port 104, tluid in said bore 187 is free to pass to exhaust 'and therefore cannot impede displacement of the `shuttle valve. Apart from the last-mentioned series of ports and bores, the wholesystem yis now under full duid pressure. it is, however, to be observed that the pistons 185, 136 of the shuttle valve 179 present difierential areas to the -fluid acting on the inner or opposed surfaces. The actual diameters in .the illustrated embodiment are respectively .625 Eand .65, and yallowing for the central shank the areas exposed to the fluid are respectively .V196 inch and .22 sq. inch. Thus, on the interconnection of the grooves -17 0 and `171 in the bush 128, the shuttle valve is displaced tothe other end of its housing.

In this position of the shuttle valve 179, the tluid supply port 105 is put into communication with the Working chamber 126, by way of bore 182 in the housing 175, while the working chamber 127 is put into communication with the exhaust port 104 by w-ay of the right hand transverse port 183 in said housing. Thus, the piston 120 -is driven outwards, and the piston 121 is driven inwards by the fluid in the balance chamber so that its associated hammer 103 is caused to strike the ranvil 106. As the piston 121 moves -inwards towards its inner limit, the reduction =196 in piston rod 115 .puts the middle groove 1711 of bush 129 into communication with the inner groove 170. By this communication, fluid is caused to pass from the supply port through grooves 171, 170 and their associated radial ports, drilling 161 in the cylinder block and drillings 193, 192 in the valve end cap 188 to the bore 187 in the suttle valve. This bore has in the illustrated embodiment a cross-sectional Aarea of .049 sq. inch, so that the diiterential .area of the shuttle valve pistons is over-balanced, .and said valve is displaced back to its illustrated position.

In the movement of the piston y121 from its inner limit to its mid-position 4as illustrated, for completion of the cycle, the supply port 105 now being again in communication with working cha-mber 127, initial displacement of piston lrod 1115 seals fluid under pressure in the bore 187 of the shuttle valve.

In the event that off-set port 104 is connected to hydraulic fluid supply and central port 105 is connected to exhaust, the tool will operate in `similar manner. Assuming both pistons to be at mid-stroke as shown in FIG. 3A and the shuttle valve 179 to be in the position shown -in FIGS. 4A and 11, working chamber 126 i-s connected to supply and working chamber 127 to exhaust. The piston 120 is therefore urged outwards by Ithe fluid supply while piston 121 is urged inwards by the fluid trapped in the balance chamber 118, 119, 123. As the piston 121 approaches its inner limit, the reduction 196 i-n piston rod puts the bore 187 of the shuttle valve, through the drillings in valve head cap 188, drilling 161 in the cylinder block, and annular groove 170 in bush 129, with exhaust port 105. This enables the pressure of the hydraulic iiuid, which is also 4operative upon the closed right hand end of shuttle valve 179, to displace said valve to the other end of its housing, putting the supply port 104 into communication with working chamber 127 by way of righ-t hand port 183 in the valve housing i175, and Working chamber 126 into communication with exhaust port 105 by way of bore 182 in said housing. Piston 121 is thus urged outwards by the supply fluid while piston is urged inwards by tltd in the balance chamber.

As the piston 120 approaches its inner limit, it puts the supply port 104 into communication, by way of the middle groove 171 and its associated radial ports 173 in bush 128, through the reduction 196 in piston rod 114, with the inner annular groove in said bush 128 and thence through duct 161 and the drillings in valve head cap 188 with bore 187 in shuttle valve 179. The fluid pressure is thus operative on the whole area of the larger piston 186 of said valve, and the diferential over the area of the smaller piston 185 causes the shuttle valve to be displaced back to its illustrated position. Thereby the Working chambers 126 and 127 are again put into communication respectively with supply port 104 and exhaust port 105.

The cylinder block 124 incorporates means whereby the correct quantity of hydraulic iluid is at all times automatically maintained in the balance chamber 118, 119, 123, so as to ensure that both pistons 120, 121 perform their full strokes in opposite directions simultaneously. In the event that the piston 120 has not been driven to its inner limit when the piston 121 reaches its outer limit, for the reason that there is insutiicient fluid in said balance chamber, fluid under pressure in the working chamber 127 which has driven the piston 121 outwards can bypass around said piston by way of the annular enlargement 165 in cylinder 119 (which enlargement is uncovered by the inner end of the piston) and through the radial drilling 163 to the bore 157; thence after lifting the ball 216 from its seat, by way of the radial drilling 1@ to the enlargement 164- which is in communication with the transverse passage 12.1. The balance chamber having thus been supplied with liuid suiiicient to drive the piston 129 to the inner end of its stroke, no iluid can escape therefrom by way of the said bypass, since the ball 216 closes on its seat in the bore 159.

On the other hand, in the event that there should be an excess of fluid in the balance chamber, piston 120 will be driven to its inner limit before piston 121 reaches its outer limit so that the enlargement 155 is on this stroke not uncovered by the piston 121. On the reverse stroke, as the piston 121 approaches its inner limit and the reduction 196 in its piston rod enters the bore of bush 129, it momentarily puts the outer groove 167 of said bush, by way of ports 215 opening from said groove and ports 173 opening into the middle groove 171, into communication with the space in the shuttle valve housing 175 which by reason of the position at that time of the shuttle valve is in communication with the exhaust port. Thereby fluid is enabled to iiow to exhaust from the balance chamber by way of enlargement 169 in the cylinder 118, to the radial drilling 168, the longitudinal bore 159 and, displacing the ball 217 in said bore from its seat, to the radial drilling 1de which communicates with said groove 167 in the bush 129. It will be appreciated that the enlargement 158 in the cylinder 118 is left uncovered by the piston 120 on its outward stroke only when there is an excess of fluid in the balance chamber, so that said piston 120 is lagging with respect to the piston 121 on its inward stroke. As this excess of fluid is expelled (the inner face of piston 120 being subjected to the iiuid supply) the piston 120 gains upon the piston 121 until, as the piston 120 closes the enlargement 169 so that no further lluid can escape, the two pistons are again synchronised.

The two by-pass ducts 157 and 159 are thus available in the course of each working cycle to ensure that exact quantity of fluid is maintained in the balance chamber so that the two pistons work always in unison.

The cylinder block 124 also incorporates pneumatic buffer systems such that no shock is transmitted back to the supply source when during the operation of the shuttle valve 179 at the end of each stroke there is a moment when uid supply is cut off from both working chambers. This moment occurs when during the displacement of the shuttle valve its pistons 185, 186 as shown in FIG. 1l simultaneously close both passages from the bore of the valve housing 175 to the recesses 177 in said housing which communicate with the working chambers. The buffer system comprises the duplicate cylinders 198 housing each one of the flexible bags 199 and communicating as above `described with the lair pressure chambers 205. Thus, whichever of the outwardly extending bores 94 in the valve block 135 is connected to the supply source, upon a momentary stoppage of flow of fluid into the working system the air contained under pressure in one of the bags 199 is subjected to the fluid pressure by way of the associated entry bore 96, and the bag is compressed to neutralise the tendency to shock. As the shuttle valve moves further to its limit position, regardless of direction, and fluid can again enter the working system, said bag 199 expands under the pressure of the contained air, until the separator valve 292 again seats in the end of the bore 96.

Thus a tool constructed and operable as described with reference to FIGS. 3-14 will impart by the hammers 102, 103 a rapid succession of blows upon the anvil 106, which is thereby caused to exert a like rapid series of blows upon the tool 169.

By virtue of the hydraulic actuation, ineffective working strokes are avoided, and the operation of the hammers will continue positively so long as the trigger 132 remains depressed.

As stated, the use of hydraulic uid for the operation of the hammer dispenses with the requirement for an air compressor, and the hammer can be operated from any readily available source of hydraulic fluid under pressure, such as the hydraulic system of a tipping lorry which will usually be present at any site where digging is required. Such use of a hydraulic system of a lorry can be facilitated by the provision of a suitable pressure accumulator in the supply line between said system and the hydraulic percussive tool.

What we claim and desire to secure by Letters Patent 1. A hydraulic percussive tool comprising a single anvil, two hammers reciprocable to engage said anvil, two pistons each of which is connected with a respective one of said hammers, two parallel cylinders in each of which one of said pistons is located, said cylinders having on corresponding sides of the pistons intercommunicating like spaces to constitute a closed balance chamber which is filled with hydraulic fluid whereby as one piston is forced in one direction, the other piston is correspondingly forced in the other direction, and hydraulic control means whereby spaces on the opposite corresponding sides of the pistons are alternately connectable respectively with supply and exhaust ducts for hydraulic fluid. 2. A hydraulic percussive tool according to claim 1 which includes a block within which said cylinders are bored, and a single casing connected to said cylinder block, said hammers being reciprocally mounted in said casing.

3. A hydraulic percussive tool according to claim 2 in which said hydraulic means includes a shuttle valve operable to connect working chambers defined by said pistons alternately and successively to a supply of hydraulic Huid under pressure and to exhaust, and means enabling said fluid Vto act upon said valve to effect displacement of said Valve automatically from one to the other of its operative positions as said pistons approach the limits of their strokes.

4. A hydraulic percussive tool according to claim 3, in which each hammer is connected to one of said pistons by a piston rod, each of said working chambers surrounding one of said piston rods, a bush in which each of said rods is reciprocable, ports in said bush and at least one control port in said rod whereby tluid under pressure is directed to effect displacement of said shuttle valve.

5. A hydraulic percussive tool according to claim 3, in which said shuttle valve is a control valve operable at will, initially to be displaced from a third, closure position wherein it prevents access of the iluid to both of said working chambers, the operating means comprising a trigger and resilient lost motion means connecting said trigger with said valve.

6. A hydraulic percussive tool according to claim 5, in which said lost motion means comprises a spring permitting the valve to be displaced between its operative positions while preventing its displacement to said closure position until released.

7. A hydraulic percussive tool according to claim 3, in which said shuttle valve is associated with a separate control valve, and trigger means whereby said separate control valve is operable at will to permit, and when released to prevent, access ofthe iluid to said working charnbers.

8. A hydraulic percussive tool according to claim 7, which includes two plungers, two seats for said plungers, means whereby cach of said plungers is resiliently biased towards its seat, ducts between supply and exhaust ports and said shuttle valve respectively closable by one of said plungers when seated, said plungers being displaceable from their seats by ow of fluid in either direction, two blind bores in which said plungers are housed, and means serving when said separate control Valve is released to permit access of fluid under pressure from the supply source to said blind bores so that said plungers are locked by fluid pressure on their seats, and serving when the 13 separate control valve is operated to permit escape of said locking uid to exhaust.

9. A hydraulic percussive tool according to claim 5, in which said cylinder block is provided with a ported lateral face, and which includes a ported valve block secured to said face, said shuttle control valve being housed in said block.

10. A hydraulic percussive tool according to claim 7, in which said cylinder block is provided with a ported face, a ported valve block secured to said ported face, said separate control Valve being housed in said valve block, and said shuttle valve being housed in said cylinder block.

11. A hydraulic percussive tool according to claim 8, in which said cylinder block is provided with a ported face, a ported valve block secured to said ported face, intercommunicating parallel bores in saidv valve block, said separate control valve and said plungers housed in said bores, and said shuttle valve housed transversely within said cylinder block and parallel to said ported face.

12. A hydraulic percussive tool according to claim 1 which includes means whereby the correct quantity of hydraulic fluid is automatically maintained in Said balance chamber to ensure synchronized displacement of both pistons with equal full strokes in opposite directions.

13. A hydraulic percussive tool according to claim 12 which includes a bypass duct in that end of one cylinder which forms part of said balance chamber, which bypass duct is opened by the piston driven to its limit position at said cylinder end by fluid from the supply, wherby said fluid is enabled to enter the balance chamber when said chamber is not already suiciently filled to drive the other piston to its limit position at the opposite end of the other cylinder, said bypass duct including a non-return valve whereby escape of uid from the balance chamber is prevented.

14. A hydraulic percussive tool according to claim 12, in which one of the cylinders has, adjacent its end other than that end which forms part of the balance chamber,

a port which While the piston in said cylinder approaches said other end is in communication with exhaust, a bypass duct and an exit port opening from said bypass duct, the

, rod of said piston having, adjacent the piston, duct means to atord temporary connection between said ports, and the other cylinder has adjacent its end which forms part of said balance chamber an entry port to said bypass duct, so located that when the connection between said exhaust and exit ports is made before excess ud in the balance chamber permits the piston in said other cylinder to close said entry port, said excess uid is enabled tov escape from said balance chamber to exhaust, the bypass duct including a non-return valve whereby entry of fluid to the balance chamber is prevented.

15. A hydraulic percussive tool according to claim 1, which includes pneumatic butler means, adapted to absorb shocks in the hydraulic fluid supply system when said hydraulic control means, in operation to change over the connections of the Working chambers between exhaust and supply, momentarily closes both connections.

16. A hydraulic percussive tool according to claim 15, in which said buffer means comprises at least one chamber in the cylinder block, a exible bag housed in said chamber and lled with air under pressure, said chamber being subjected to the pressure of the hydraulic fluid supply.

Reerences Cited by the Examiner UNITED STATES PATENTS 455,905 7/91 Thomson 173-101 480,223 8/92 Tremain 91--155 604,502 5/98 Reynolds 91--193 706,688 8/02 Reynders et al. 91-4 1,152,624 9/15 Gilman 91-130 FOREIGN PATENTS 830,332 2/52 Germany.

BROUGHTON G. DURHAM, Primary Examiner. f

KARL I. ALBRECHT, Examiner. 

1. A HYDRAULIC PERCUSSIVE TOOL COMPRISING A SINGLE ANVIL, TWO HAMMERS RECIPROCABLE TO ENGAGE SAID ANVIL, TWO PISTONS EACH OF WHICH IS CONNECTED WITH A RESPECTIVE ONE OF SAID HAMMERS, TWO PARALLEL CYLINDERS IN EACH OF WHICH ONE OF SAID PISTONS IS LOCATED, SAID CYLINDERS HAVING ON CORRESPONDING SIDES OF THE PISTONS INTERCOMMUNICATING LIKE SPACES TO CONSTITUTE A CLOSED BALANCE CHAMBER WHICH IS FILLED WITH HYDRAULIC FLUID WHEREBY AS ONE PISTON IS FORCED IN ONE DIRECTION, THE OTHER PISTON IS CORRESPONDINGLY FORCED IN THE OTHER DIRECTION, AND HYDRAULIC CONTROL MEANS WHEREBY SPACES ON THE OPPOSITE CORRESPONDING SIDES OF THE PISTONS ARE ALTERNATELY CONNECTABLE RESPECTIVELY WITH SUPPLY AND EXHAUST DUCTS FOR HYDRAULIC FLUID. 